Solid state power amplifiers used in satellite communication systems are accessed from ground station terminals. There is a risk of potentially uncontrolled uplink power which could overdrive the gallium arsenide FET output devices in the solid state power amplifiers. These FET devices are sometimes referred to as MESFET (metal semiconductor) devices. The solid state power amplifiers on the satellite are adapted to receive certain ranges of input power. Higher ranges of input power can occur after, for example, the ground stations have increased the amount of input power to correct for conditions, such as rain conditions, which degrade the input power and these terminals are not turned back immediately when the weather conditions change. The extended overdrive can degrade the solid state amplifier reliability due to excessive gate currents induced from the incoming microwave signal. These FET devices utilize very narrow (on the order of 0.5 micron) gate metal structures which can be damaged from excessive current density.
It is therefore desirable to provide some means at the satellite, i.e., at the amplifier, to sense the onset of excessive gate current and to limit the microwave power applied to the amplifier before any damage (reliability degradation) threshold is exceeded.